Rehabilitation of Indigenous Browse Plant Species Following Exclosure Established on Communal Grazing Lands in South Tigray

Atsbha et al. Ecological Processes (2019) 8:43 https://doi.org/10.1186/s13717-019-0197-1

RESEARCH Open Access Rehabilitation of indigenous browse plant species following exclosure established on communal grazing lands in South Tigray, Ethiopia, and implication for conservation Tesfay Atsbha*, Solomon Wayu, Nguse Gebretsadkan, Tesfay Gebremariam and Tsgehiwet Giday

Abstract Background: Despite the wide use of indigenous browse plant species, there is almost no information on the rehabilitation of indigenous browse species following area exclosure (AE) established on communal grazing lands (CGL) in Southern Tigray. The objectives of this study were to assess the rehabilitation of browse plant species following AE establishment on CGL. A total of 61 and 59 plots of 10 × 10 m2 size were laid down at 50-m intervals along parallel line transects at AE and GCL, respectively. Data collected on vegetation attributes were subjected to analysis of t test (unequal variances) using R-software. Results: The Shannon diversity index of the browse plant species was 1.25 and 0.81 in AE and CGL, respectively (P < 0.001).TheoverallpopulationstructureofbrowseplantspeciesintheAEshowsareverseJ-shapedpopulationcurveand “good” regeneration status, which reveals that the future communities may be sustained. Leaf biomass and basal area of browse plant species were significantly higher in the AE than in CGL (P < 0.001). After exclusion of grazing, AE was found to have positive effects on diversity and aboveground biomass of browse plant species. Conclusions: The study gives an understanding of the diversity, the pattern of population and regeneration of the browse plant species, which may help in the management and conservation of the species. Our results indicate that grazing exclusion is an effective management strategy to restore browse plant species. We concluded that the establishment of AE had a positive effect on the rehabilitation of browse plant species diversity and improved population structure and regeneration potentials of degraded grazing lands. Long-term monitoring and evaluation systems will be required to gain an informed understanding of the roles played by area exclosures in the rehabilitation and conservation of browse palnt species diversity. Keywords: Browse, Rehabilitation, Restoration

Background communities and over-browsing by livestock and game Browse plants, beside grasses, constitute one of the animals (Abule et al. 2005). As a result, encroachment cheapest sources of feed for ruminants (Ahamefule et al. by weeds and undesirable plants, which are plant species 2006). Particularly, fodder trees and shrubs could play that are classified as undesirable, noxious, injurious or both ecological and economic roles in livestock produc- poisonous like Lantana camara L. and Prosopis juliflora tion systems (Karki and Goodman 2009). However, the (Sw.) DC (Allen and Allen 1981; Asfaw and Thulin extensive utilization of the browse plants has increased 1989), has become a threat to the livestock production pressure on the native vegetation, resulting in degrad- systems in the Horn of Africa, especially in Ethiopia ation of the resources due to over-utilization by the (Amaha 2003; Gemedo et al. 2006). Gebremedhin (2000) stated that the misuse of natural resources has resulted in very serious land degradation in most places. Improv- * Correspondence: [email protected] Tigray Agricultural Research Institute, Alamata Agriculture Research Center, ing the management of the natural resources providing P.O. Box 56, Alamata, Ethiopia

© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Atsbha et al. Ecological Processes (2019) 8:43 Page 2 of 9

ecological services (soil formation, nutrient cycling, and rehabilitation of indigenous browse species following ex- primary production (Alcamo, 2003; Zerihun et al. 2002); closure established on communal grazing lands in South gully stabilization, controlling accelerated soil erosion, Tigray, Ethiopia. reducing flood damage (Nedessa et al. 2005; Wolde et al. 2007) and immediate economic needs are the major re- Materials and methods search and development challenges for the degraded Description of the study area areas of northern Ethiopia in particular and drylands of The study was conducted in the South zone of Tigray se- East Africa in general. lected districts. It is located at 680 km North of Addis A common restoration practice in Ethiopia is the use of Ababa, the capital city of Ethiopia and 180 km South of area exclosure (AE) (Tekle 2001; Tekle and Bekele 2000; Mekele, the capital city of the Tigray regional state. The Asefa et al. 2003;Teferaetal.2005). In the current study, zone consists of five administrative districts, namely Raya we distinguished between small-scale exclosures used for Alamata, Alaje, Endamohoni, Ofla and Raya Azebo. The protecting livestock grazing (Desta and Oba 2004)andthe study was conducted at five sites (Raya Alamata, Emba large-scale multi-purpose degraded areas protected from Alaje, Endamohoni, Ofla and Raya Azebo) (Fig. 1). The human and livestock exploitation. Restoration of biodiver- sample of different sites was selected with the aim of sity using AE has not been evaluated in terms of the ef- encompassing a wide range of ecoregional diversity. The fects of management factors (i.e. AE versus communal Southern Tigray Zone is one of the seven zones of the re- grazing land (CGL)) on indigenous browse plant species gion bordering to the South and West with Amhara (BPS) diversity. We evaluated the restoration of BPS diver- Regional State, to the North with a South Eastern zone of sity in highly degraded mountain landscapes in Southern Tigray and to the East with Afar Regional State. Geo- Tigray, which were previously used for farming and com- graphically, it is located between 12° 15′ and 13° 41′ north munal grazing. latitude and 38° 59′ and 39° 54′ east longitude with an In the places where AE are established, particularly in the altitudinal range of 1350–3925 m.a.s.l. Based on the trad- southern part of the region, area exclosures are among the itional classification system, Southern zone covers Kola, green spots with considerable species diversity (Tefera et al. Weynadega and Dega agro-ecologies that enable to grow 2005; Betru et al. 2005). In exclosures, it is generally be- varied types of crops, livestock and tree species. It covers lieved that all the land resources will be protected from an area of 9446 km2 with a total population of 538,422. degradation. Although the restoration effects of AE have The Southern zone has experienced two rainfall seasons: been well studied (Kindeya 2003; Aerts et al. 2004; the short rainy season locally known as “Belgi” that occurs Descheemaker et al. 2006), chemical composition and usually from February to April and the main rain season digestibility of some browse plant species (Ammar et al. locally described as “Kiremti” that comes during June to 2004;Ahamefuleetal.2006; Melaku et al. 2010; September. On average, the area receives annually about Boufennara et al. 2012;Girmaetal.2015; Weldemariam 600 mm rainfall with a mean annual temperature of 25 °C. and Gebremichael 2015) and use and availability of tree The dominant soil types of the area are Vertisol, Fluvisols, and shrub resources (John and Moses 2005; Teferi et al. Luvisols and Cambisols, which implies the need for site- 2008), whereas there is no study that offers quantitative in- specific management practices to improve the productivity formation that helps to compare AE with the unprotected of the land (Kidane et al. 2016). areas with respect to browsing plant species restoration. In addition, in the Tigray region, Northern Ethiopia, some of Site selection and sampling procedure the studies conducted earlier (Gebremedhin 2000;Emiru A reconnaissance survey was conducted in the second et al. 2002; Kindeya 2003; Aerts et al. 2004; Tefera et al. week of September 2018, to collect baseline information, 2005; Muluberhan et al. 2006; Yayneshet et al. 2009;Wolde observe vegetation distribution and determine the num- and Aynekulu 2011, Wolde et al. 2011b, 2011c; Yayneshet ber of transect lines to be laid. The CGL was located 2011;WoldeandMastewal2013;Tsegayetal.2019;Tesfay 0.5–1 km away from the AE. It is assumed that the AE et al. 2019) were specifically trying to estimate the role of and CGL were homogenous in biophysical factors before AE in the recovery of woody vegetation diversity without the AEs are restricted for rehabilitation and are similar considering specifying indigenous browse species. It is very in topographic and climatic characteristics. The AE was important to have basic information to browse plant species established since 2004 and covers a total area of 500– diversity and biomass production, as these may facilitate 1500 ha, while the CGL covered 200–1300 ha (Southern the efficient and effective use of rangeland resources as live- Zone BOARD 2018). Adjacent to this AE, there is CGL stock feed. Therefore, this study was initiated to generate used by the community with no restriction to access re- quantitative information and thereby to evaluate whether source. Therefore, this study was conducted in these two AE has an impact on the density and diversity of BPS. land-use systems: AE having the restriction and rules of Thus, the objectives of this study were to assess resource access, in which people and grazing animals are Atsbha et al. Ecological Processes (2019) 8:43 Page 3 of 9

Fig. 1 Map of study area (location of study site) permanently kept outside this area, and the nearby CGL species in the field, vernacular names from key infor- having no restriction and rule of resource access. The mants were used and the specimens supported by vou- CGL areas were considered controls, while the AE repre- cher specimens by referring to Edwards et al. (2000) and sented rehabilitation. Hedberg et al. (2006). The important quantitative analysis such as important value index (IVI) of indigenous browse species was determined as in Curtis and Data collection McIntosh (1950). After the identification of plant species, which are Basal area was calculated using DBH as follows: Basal browsed by animals, data were collected for quantitative area of a tree = D2/4 , where D = diameter and = analysis. Since the study area has different formation 3.14. Browse species diversity was calculated based on types, stratified sampling design, as described by Krebs the number of species and their abundance,P according to (1989) was used to collect data on vegetation. A total of H 0 ¼ − s Pi ðPiÞ; Kent and Coker (1992): i¼1 ln where 120 (10 m by 10 m as recommended by Kent and Coker H′ = Shannon diversity index, S = the number of species, (1992)) plots were established. The total number of plots Pi = proportion of individual species and InPi = natural inside AE and outside AE were 61 and 59, respectively. ′ log. Equitability ðevennessÞ¼ H where H′ = Shannon In each plot, all woody species with a diameter at breast H max S H height (DBH) ≥ 2.5 cm and height ≥ 1.5 m were recorded. diversity index, = the number of species and max = Within the major plot of 100 m2, five sub-plots, each 5 the maximum level of diversity possible within a given m × 5 m (25 m2), were set up to collect vegetation data population. of shrubs with a diameter at stump height (DSH) ≥ 1.5 The population structure of each of the browse plans cm and height ≥ 0.5 m and the mean of these five sub- species in each of the two study sites was assessed plots were used in the analysis. through grouped arbitrarily into height classes and Seedlings were recorded for analysis of the regener- diameter classes (Emiru et al. 2002). Regeneration status ation status of trees within each 25-m2 sub-plot. In this of the study area was analysed by comparing saplings study, all individuals with a height between 0.01 and 1 m and seedlings with the matured trees according to were considered seedlings of trees, and both height and Dhaulkhandi et al. (2008) and Tiwari et al. (2010). The diameter measurements were taken (DBH < 2.5 cm and leaf biomass of a tree was estimated by using the model height < 1 m). Within each 25-m2 sub-plot, five 1 m × 1 of Petmak (1983): - logW = 2.24 logDBH-1.50, where m sub-plots were used to collect data on seedlings W = leaf biomass in kilograms of dry weight and DBH (below a height of 0.1 m) of shrubs. For identification of (diameter at breast height) at 130 cm height and the leaf Atsbha et al. Ecological Processes (2019) 8:43 Page 4 of 9

biomass of a shrub was estimated by the equation: - logW = 2.62 logDS-2.46, where DS is the stem diameter (cm) at 30 cm height. The model was adopted because it is established in northeast Thailand with similar climatic and topographic conditions in the study area. The argu- ment claims similarities between climate and topography because climate and topography are among the most important drivers of broad-scale patterns of species (Irl et al. 2015; Moura et al. 2016). Climate can affect species composition indirectly via their effects on vegetation Fig. 2 Life form distribution of plant species (AE area exclosure, CGL (Stein et al. 2014), while topography can interplay with communal grazing land, Mesopha mesophanerophyte, Micropha both climate and vegetation, also affecting species rich- microphanerophyte, Nanopha nanophanerophyte) ness (Ruggiero and Hawkins 2008; Stein et al. 2014). In addition, this was developed in the woodland and agricultural trees with 98% of trees having a DBH less than 2.5 cm were 51.81 and 23.14 m2/ha in AE and CGL, re- 40 cm (similar with the study area). spectively. Basal area (BA) of the browse plant species was significantly larger in the AE compared to the CGL Data analysis (P < 0.001) (Table 2) (Additional file 1). The mean leaf t test unequal variance using R-software version biomass of browse plant species at the AE and CGL was 3.5.1 (The R Core Team 2018) was employed to test the 753.68 and 485.57 kg/ha, respectively. In addition, the significance of differences of species richness, diversity mean leaf biomass of browse plant species was signifi- index, species evenness, basal area and estimation of leaf cantly lower in the CGL compared to the AE (P < 0.001) biomass of browse plant species of the two land-use (Table 2). systems. Population structure of browse plant species Results The diameter class distribution of browse plant species Browse species composition in the AE reflected reversed J-shape (L-shape). This The floristic composition can be described in terms of means species frequency distribution had the highest species richness, abundance, dominance and frequency. frequency in the lower diameter and height classes and a In the floristic analysis, 64 plant species belonging to 52 gradual decrease towards the higher classes (Fig. 3). genera and 37 families were identified in AE. The life Similarly, the density distribution of browse individuals form distribution of these species were 22 (34.38%) in different height classes also showed a similar pattern mesophanerophyte, 25 (39.06%) microphanerophyte, 13 with diameter classes at the AE. However, the height dis- (20.31%) nanophanerophyte and 4 (6.25%) climbers. On tribution for the CGL shows a bell-shape, which showed the other hand, 43 plant species belonging to 34 genera there was a higher number of individuals in the middle and 25 families were identified in CGL. The life form height classes but decrease towards the lower and higher distribution of these species were 16 (37.21%) mesopha- height classes (Fig. 4). nerophyte, 17 (39.53%) microphanerophyte, 9 (20.93%) nanophanerophyte and 1 (2.33%) climbers (Fig. 2). Regeneration status of browse plant species Species diversity, richness and evenness The composition and density of seedlings and saplings The value of the Shannon diversity index of browse indicate the status of regeneration in the study area. Ac- plant species in the AE and CGL was 1.25 and 0.81, re- cording to Dhaulkhandi et al. (2008), the density values spectively, indicating significantly lower browse species of seedling and saplings are considered as regeneration diversity in the CGL than the AE (p < 0.001). The aver- potential of the species. According to Khumbongmayum age number of individuals per hectare (ind/ha) was also et al. (2006), Dhaulkhandi et al. (2008) and Tiwari et al. higher in the AE (3481) than in the CGL (2040) (p < (2010), the regeneration status of the browse plant spe- 0.001). The species evenness also showed significant dif- cies at AE is considered as good regeneration because ferences (p < 0.05) between the two land-use systems density of individuals of species showed that the sapling (Table 1). (37.03%) > seedling (26.16%) < matures (36.82%). Based on the criteria of Khumbongmayum et al. (2006), Dhaul- Basal area (BA) and leaf biomass of browse plant species khandi et al. (2008) and Tiwari et al. 2010, the CGL was The mean basal area (expressed as the basal area of categorized under fair regeneration (mature > sapling > stems per hectare) of browse plant species with DBH > seedling) (Fig. 5). Atsbha et al. Ecological Processes (2019) 8:43 Page 5 of 9

Table 1 Species composition and diversity (mean + SE) of area exclosure and adjacent communal grazing land at southern Tigray Land-use system Sample size Density (ind/ha) Species richness Shannon diversity index Evenness AE 61 3481 + 288 4.72 + 0.18 1.25 + 0.04 0.84+ 0.02 CGL 59 2040 + 265 2.89 + 0.13 0.81 + 0.04 0.77 + 0.02 P value *** *** *** * SE standard error, AE area exclosure, CGL communal grazing land ***Significant difference at the 0.001 level *Significant difference at the 0.05 level

Discussion vulnerability of the plant species by animals and/or hu- Browse species composition man intervention at maturity or early stage of The wood species composition recorded in the AE site is regeneration. higher than that in the CGL. This study revealed that The vegetation composed of the browse plant species the vegetation composition of the AE was much denser was denser in the AE than in the CGL. The density of than that of the CGL. The difference observed in woody woody vegetation was significantly affected by grazing, species composition between the two land-use systems i.e. a higher density of woody species was observed on showed the positive effect of AE through proper conser- exclosure site than in the communal grazing sites (Au- vation strategies like rehabilitation. Similarly, encour- gustine and McNaughton 2004; Teshome et al. 2009). aging results have been reported from studies made on This indicates that AE influenced both species richness exclosures established in Tigray, Ethiopia (Emiru et al. and density. The present result agrees with the same 2002; Tefera et al. 2005; Tesfay et al. 2019). Sisay et al. previous study in Ethiopia, like Muluberhan et al. (2006), (2001) and Tessema et al. (2011) also suggested that Yayneshet (2011) and Gebrewahd (2014). The species heavy grazing might cause a reduction of plant species evenness also showed significant differences (p < 0.05) composition over time. Due to the high and frequent between the two land-use systems (Table 1). This might disturbance by animals and human interference, the indicate that the existence of variations in species diver- number of seedlings of browse plant species was low in sity was a result of the heterogeneous distribution of the CGL. species due to protection vegetation establishment factors. A low evenness value means that there is the dom- Species diversity, richness and evenness inance of one or more species in the community, while The value of the Shannon diversity index of browses high evenness means that there is a uniform distribution plant species in the AE and CGL was significantly differ- among the species in samples, demonstrating that indi- ent (p < 0.001). This could result from repeated habitat viduals are well distributed (Cavalcanti and Larrazábal disturbances in the CGL due to frequent and intensive 2004). In agreement with the above statements, the interference of both humans and livestock for grazing browse plant species in the AE was more uniformly dis- and other communal uses. Decline in browse species di- tributed than that in the CGL. versity in the grazing land could be a result of the loss of seedlings of some species unable to establish at an early stage of development, and selective defoliation and trampling by grazing herbivores (Belaynesh 2006) or either harvested at their early age by the local inhabitants or their domestic animals (Wondie et al. 2014). Accord- ing to Kibret (2008), the reduction of species diversity in the CGL could be an indication of the increased

Table 2 Leaf biomass and basal area (mean + SE) of area exclosure and adjacent communal grazing land at southern Tigray Land use system Sample size Basal area (m2/ha) Leaf biomass (kg/ha) AE 61 51.81 + 6.98 753.68 + 47.68 CGL 59 23.14 + 3.16 485.57 + 41.41 Fig. 3 Diameter class frequency distribution of browse plant species P value *** *** at both land-use systems. (DBH class: 1 = <5cm,2=5.1–9cm,3=9.1– SE standard error, AE area exclosure, CGL communal grazing land 13 cm, 4 = 13.1–17 cm, 5 = 17.1–21 cm, 6 = 21.1–25 cm, 7 = >25.1cm) ***Significant difference at the 0.001 level Atsbha et al. Ecological Processes (2019) 8:43 Page 6 of 9

important disturbances resulting in rangeland degradation and environmental problems (Bellows 2003; Amiri et al. 2008; Darkoh 2009; Suizi et al. 2019). It has been suggested as the main cause of biodiversity loss (Scholes and Biggs 2005). In particular, excessively heavy grazing has been indicated to contribute to decline in biodiversity (Biggs et al. 2008). Besides, Tsegay et al. (2019) also reported that accumulation of vegetation biomass de- clined with grazing land degradation and change in species composition, leading to a less biomass production at a higher grazing pressure compared to lower grazing Fig. 4 Height class frequency distribution of browse plant species at pressure. Grazing is one of the main land uses of natural – – land-use system. (Height class: 1 = < 4 m, 2 = 4.1 6m,3=6.1 8m,4= rangelands and affects the species composition and plant 8.1–10 m, 5 = 10.1–12 m, 6 = 12.1–14 m, 7 = 14.1–16 m, 8 = >16.1m) biomass (Klein et al. 2007; Post and Pedersen 2008). Both plant productivity and species diversity will in- Basal area and leaf biomass of browse plant species crease under appropriate grazing intensity (Proulx and BA of browse plant species in the AE and CGL showed a Mazumder 1998). However, overgrazing is considered to significant difference (P < 0.001). This variation may come be the main cause of natural grazing land degradation from the differences in the management practice of the (Ma et al. 2019). Grazing reduces the aboveground bio- study sites. The basal area of the browse plant species in mass of vegetation but quickly recover after implementa- the study area was low in CGL, indicating the browse tion of AE (Sasaki et al. 2008; Frank et al. 2002). plant species were thin in the CGL. The great difference According to Witt et al. (2011), woody biomass increases in basal area between the AE and CGL could be due to with grazing exclusion due to the regeneration potentials the high number of multi-stemmed trees in the AE, lead- of tree and shrub species. Likewise, some studies (Ver- ing to bigger diameters. The management practices, basal doodt et al. 2010; Wesche et al. 2010) showed that bio- area, species richness, the number of individuals per hec- mass of woody vegetation improved following the tare and species diversity were the probable reason for the establishment of grazing exclosure on communal grazing differences in the leaf biomass among the two land-use lands, which might be due to the higher abundance and systems. For instance, Raju (2012) found that the basal density of woody vegetation. The pressure of livestock area is an important parameter, which determines the bio- grazing and overall utilization of rangelands has caused mass by the species. The more basal area indicated the vegetation degradation (Amiri et al. 2008). more biomass. In the current study, AE had a significant difference in Population structure of browse plant species brows plant species biomass over the CGL. The lower Girth class frequency showed a reverse J-shaped popula- leaf biomass in CGL compared to the AE in our study tion curve in AE which is dissimilar to CGL (a bell- could be due to continuous heavy grazing, which nega- shape). The possible reason for decreasing percentage of tively affects the growth of browse plant species. This the number of individual browse species within the lar- finding is in line with Yayneshet et al. (2009) who re- gest diameter class (> 25.1 cm) might be due to the il- ported that more than double biomass was produced legal cutting system used by the local people for under AE than CGL in the highlands of the Tigray re- construction materials and fuelwood consumption. This gion of Ethiopia. Overgrazing is one of the most result is in line with the study made by Getaneh (2007) and Tefera et al. (2015), who showed that woody species with large diameter were harvested by the local people for construction and charcoal preparation. The presence of heavy browsing leads to skewed age structure, small seedlings being dominant in the grazed areas (Butler and Kielland 2008). Similarly, the density distribution of browse individuals in different height classes also showed a similar pattern with diameter classes at the AE. However, the height distribution for the CGL shows a bell-shape, according to Feyera et al. (2007), the bell-shape pattern indicates a Fig. 5 Regeneration status of browse plant species at both land-use poor reproduction and recruitment of species. Protec- systems (AE area exclosure, CGL, communal grazing land) tion influenced the height class distribution of the Atsbha et al. Ecological Processes (2019) 8:43 Page 7 of 9

woody vegetation attributes (Butler and Kielland 2008; any species are more vulnerable to any kind of environ- Yayneshet 2011). The low proportion of lower and mental stress and anthropogenic disturbance (Iqbal et al. higher height classes is probably because of grazing/ 2012; Moumita and Ashalata 2014). Besides, the decline browsing or trampling and shows that the CGL had a in species diversity in the communal grazing land could lower potential for rehabilitation of browse plant species be a result of the loss of seedlings of some species un- than the area enclosed. A reversed J-shape distribution able to establish at an early stage of development, and of height/diameter classes in our study indicated a con- selective defoliation and trampling by grazing herbivores tinuous and good regeneration and/or a stable popula- (Belaynesh 2006). tion of browse plant species. In contrast, bell-shaped distribution of browse plant species in the CGL indi- Conclusion and recommendation cated a hampered regeneration status, which might be The overall population structure of tree species in the due to several disturbance factors, including deforest- study site reveals that the contribution of seedlings to ation by local people in addition to frequent browsing the total population was the highest, followed by sap- and trampling by livestock. lings and adult trees. It shows regeneration of browse plant species in the AE is “good” and the future commu- Regeneration status of browse plant species nities may be sustained unless there is any major envir- The composition and density of seedlings and saplings onmental stress or interference exerted by human indicate the status of regeneration in the study area. Ac- activities. However, considering the increasing anthropo- cording to Dhaulkhandi et al. (2008), the density values genic pressure, there may be a spatial and temporal of seedling and saplings are considered as regeneration threat to the seedling establishment and growth of potential of the species. In general, the regeneration of browse plant species in the study site. The growth, sur- species is affected by various anthropogenic factors and vival and reproductive potential of the browse plant spe- natural phenomena (Iqbal et al. 2012). The overall re- cies will be at risk in the near future if the present trend generation status of the browse plant species of the AE of anthropogenic continues at CGL. The present study and CGL site is satisfactory at community level showing has demonstrated that grazing prevention is an import- good and fair regeneration status, respectively. These re- ant means of rehabilitating and renovating browse plant vealed that the high level of protection in the area helps species. Quantitative analysis of diversity, population ’ the regeneration of browse species. Woody species ap- structure and regeneration status of browse plant species pearance in AE indicates a long period of protection, recorded from the present study may provide baseline allowing regeneration of shrubs and trees (Kebrom 2001; information for livestock feed resource projects, for Tefera et al. 2005). However, in the CGL, a low level of evaluation of whether the AE establishment should be protection in the area helped the regeneration of browse expanded and for policymakers to take into account the plant species. The low proportion of seedlings in the value of AE in their management decisions. CGL showed the browse plant species rehabilitation has been continuously restricted by disturbance, such as, overgrazing and human activity. According to this data, Supplementary information Supplementary information accompanies this paper at https://doi.org/10. most of the seedlings perished off before reaching sap- 1186/s13717-019-0197-1. ling and mature stages for various reasons, which might be due to grazer and browser pressure (Teshome et al. Additional file 1: Table S1. Density (D), basal area (BA), biomass (kg/ha) 2015). The relatively better/lower regeneration of browse and regeneration status of browse plant species of area exclosure in the south Tigray. Table S2. Density (D), basal area (BA), biomass (kg/ha) and plant species might be attributed to the density of their regeneration status of browse plant species of communal grazing land in mature trees, maybe due to the presence/absence of sig- the south Tigray. nificant amounts of viable seeds in the soil and/or the wide dispersal of their seeds through ungulate feces Abbreviations (Anteneh et al. 2011). According to Taye et al. (2002), a AE: Area exclosure; BPS: Browse plant species; CGL: Communal grazing land tree species with no seedling and sapling in natural vegetation is under a risky condition and it is suggested that Acknowledgements these species are under threat of local extinction. We would like to acknowledge the Tigray Agricultural Research Institute for financial support to do the research. We would also like to thank the local Species under not regenerating condition might have community of the study area. occurred due to an existing disturbance at the study site like grazing, firewood collection and poor biotic poten- Authors’ contributions tial of tree species, which either affect the fruiting or All authors contributed to the development of the concept and implementation of the study. TA, NG, TGe, and TGi carried out field data seed germination or successful conversion of seedling to collection and data analysis and drafted the manuscript. All authors revised sapling stage. Moreover, individuals in young stages of the manuscript and read and approved the final version. Atsbha et al. Ecological Processes (2019) 8:43 Page 8 of 9

Funding ne II) com ênfase em CopepFicus sycomorous (Crustacea). Revista Brasileira No funding was received de Zoologia 21(3):467–475 Curtis JT, Mcintosh RP (1950) The interrelations of certain analytic and synthetic Availability of data and materials phytosociological characters. Ecology 31(3):434–455 The dataset(s) supporting the conclusions of this article is (are) available in Darkoh MBK (2009) An overview of environmental issues in southern Africa. Afr J the supplement materials. Ecol 47(Suppl. 1):93–98 Descheemaker K, Nyssen J, Rossi J, Poesen J, Mitiku H, Moeyerson J, Deckers J Ethics approval and consent to participate (2006) Sediment deposition and pedogenesis in exclosures in the Tigray Not applicable Highlands, Ethiopia. Geoderma 132(3–4):291–314 Desta ZH, Oba G (2004) Feed scarcity and livestock mortality in enset farming – Consent for publication systems in the Bale highlands of Southern Ethiopia. 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